Primary Temporal Position (PTP) is the term used to reference your position in real time, compared to your relative timeline. The PTP is your position when you experience time at a 1:1 scale, and is the 'proper' place that you should be in the timeline. With time machines it is possible to travel in either direction along the timeline instantly.
In-story (Character) PTP
The PTP of a character is the point in time they were at when they started a time jump. Some time machines will automatically send a traveler back to their own PTP after running out of power.
Meta (Audience) PTP
The PTP for the audience in general is the most recent update, while the PTP for a new reader is the latest page they have read. (When a new reader finishes archive binging for the first time, they will have caught up to everyone else's PTP.)
Because ANL is a time-travel story in which characters can change their own pasts, if you try to re-read the archives from a later PTP, you may notice slight -- or even drastic -- changes in the story. Previously, the archive had a button to toggle between "new" and "retconned" versions of a page. Right now the only way to return to the "new reader" version of a page is to use the "Reset Temporal Position" button, which reverts your PTP to the page you're currently on. (Be warned that if you do this, your progress will be reset and you will miss out on later retcons as you continue through the archive!)