---
title: Vocabulary
description: What each word means in PostbackX, including the four that mean something different in the rest of the industry.
updated: 2026-07-30
order: 1
related: [/concepts/attribution, /guides/first-campaign]
---

Ad tracking has a vocabulary problem: the same word means different things at
different companies, and two different words often mean the same thing. This page
is the list PostbackX uses. Where the industry disagrees with us, that is noted.

## The two kinds of "source"

This is the distinction worth learning first, because both sides of your business
get called a source somewhere.

**Platform** is where your ad spend goes — the traffic side. Facebook, NewsBreak,
TikTok, Snapchat, Roku, Axon, BidSystem and Google are platforms. When a report
asks you to filter by platform, it means this.

**Offer source** is where your offers come from — the money side. It is the
affiliate platform that pays you, and the thing that sends conversions back to
PostbackX. Everflow is an offer source.

> Most of the industry calls an offer source a "network". PostbackX does not,
> because "network" also names an ad placement (Facebook's Audience Network) and a
> traffic partner. The REST API still uses `network_id` and `network_name` in field
> names for historical reasons — the field is an offer source.

## Traffic, in order

**Campaign** — the thing that ties everything together. A campaign takes a pixel,
an offer and optionally a flow, and gives you one tracking link. Every click,
conversion and pixel event that follows is attributed through it.

**Click** — one visit to your tracking link. PostbackX records it, assigns it a
**click id**, and redirects the visitor onward. The click id is the thread that
the whole system pulls on later; see [attribution](/concepts/attribution).

**Offer** — what you are promoting, and where the visitor converts. It has a
destination URL and a payout.

**Landing page** — a page of your own that the visitor sees before the offer.
Worth using when you want to warm the visitor up, or when you need Facebook's
browser cookies (`_fbp` and `_fbc`), which can only be read client-side and
materially improve Facebook's match quality.

> The code and some report titles say "lander". Same thing.

**Flow** — a reusable routing rule: which landing pages and offers traffic should
be split across, and in what proportion. Define one, use it in many campaigns,
change it once and every campaign follows. Sometimes called a funnel.

**Direct link** — the alternative to redirecting. Your ad points straight at your
landing page, and a JavaScript snippet creates the click record from the page
itself. Use it when you want full control of the URL in the ad, or want to avoid
redirect latency. See [tracking snippets](/reference/snippets).

## Money, in order

**Conversion** — the visitor did the thing: submitted a form, bought, called.
Your offer source tells PostbackX by calling a
[postback URL](/reference/postback).

**Payout** — what you earn for one conversion. Revenue is payout summed.

**Spend** or **cost** — what the ad platform charged. Synced automatically from
each connected platform.

**Transaction id** — the offer source's own id for a conversion. PostbackX uses it
to recognise a duplicate delivery, so the same conversion is not counted twice.

## Metrics

These are computed for you, everywhere, the same way. Do not recompute them from
the raw fields — if a report and your spreadsheet disagree, this is usually why.

| Metric | Definition | Reading it |
| --- | --- | --- |
| Profit | `revenue - spend` | Negative means you are paying for traffic that does not pay back. |
| ROAS | `revenue / spend` | Return on ad spend. **1.0 is break-even**, not zero. |
| Conversion rate | `conversions / clicks` | |
| EPC | `revenue / clicks` | Earnings per click. The number to compare against your CPC. |
| CPA | `spend / conversions` | Cost per acquisition. Compare against payout. |

When there is nothing to divide by — no spend, no clicks — the result is `0`
rather than an error or a blank.

## Getting conversions in and out

**Postback** — a URL your offer source calls when a conversion happens. This is
how conversions get *into* PostbackX. It carries the click id, so PostbackX knows
which click to credit.

**Pixel** — how conversions get *out* of PostbackX, back to the ad platform, so
its algorithm can optimize toward people who buy rather than people who click.
For Facebook this uses the Conversions API.

**CAPI** — Facebook's Conversions API: server-to-server conversion reporting, as
opposed to the browser pixel. More reliable, and it works when the browser blocks
things.

**Campaign mapping** — the link between a PostbackX campaign and the ad
platform's own campaign. Mapping them is what lets PostbackX put your spend and
your revenue in the same row.