Segments are a set of GA data that meets the criteria you selected. To make it clearer, an example would be combining data about visitors to the site from some strategically important city for you, a specific section of the site or when making a purchase of a specific product.
Types of data segments
A segment contains one or a number of reversible filters (that is, those that do not change the initial information).
They provide an opportunity to view information according to the categories of site visitors, sessions and hits, for example:
✓ Sessions on ads from a specific campaign, sessions with purchases;
✓ circulation of income over (...) hryvnia;
✓ users who have already made purchases or visitors who have added products to the cart.
In one segment there may be filters for sessions, users, requests.
Analytics data segment hierarchy:
Users There are all who interacted with your site or application.
Sessions. All user impacts on your resource are grouped into sessions.
Appeal. Every interaction with your resource throughout the session. These can be page views, events, e-commerce transactions, and so on.
One user can correspond to a number of sessions, and one session can correspond to a series of calls.
USER → Session → appeal.
Segments provide an opportunity to select specific information from a single mass and notice the possibilities in order to improve their work.
Example: Internet posters for cultural events throughout Ukraine have a bounce rate of around 55%.
To see the possibilities for reducing failures, see the reports. The publication found in the geolocation report that visitors from Lviv had a bounce rate of almost 80%, while visitors from other cities had less than 50%.
To understand the behavior of users from Lviv, create a segment for this city.
Now you can see which articles are read by Lviv citizens, from where they come to the site and which page they leave most often. It turned out that the residents of Lviv come to the site mainly through links from "Vkontakte" and get on the page with a description of Kiev cultural events, where they immediately leave.
Hypothesis: problem with targeting and distribution of articles in Vkontakte:
1. It is necessary to make sure that Lviv citizens rarely switch to the pages of Kiev events;
2. It is necessary to write more articles about events in Lviv. If a Lvov resident gets to the page about Kiev events, he should be offered to go to the page about events in Lviv.
This will help reduce the bounce rate and increase the number of Lviv citizens returning to the site.
Now let's create a segment according to the Support Google instructions https://support.google.com/analytics/answer/3124493?hl=en
Annotations are peculiar notes in GA reports. With their help, you can add both private and public comments, as well as charts.
For example, if your colleague has noticed some unobvious changes or if a new advertising campaign is launched - make an annotation and track the changes in traffic.
How to create annotations
1. Creating annotations through a report
Go to any of your reports. Click the small arrow in the center, as shown in the example, and select “add comment” on the right.
After that, a screen will appear where you can enter annotation text (up to 160 characters) and choose the type of privacy for the annotation.
2. Creating annotations via admin panel
If you want to add several annotations at once, it will be more convenient to do this through the admin panel.
After you select “Create a new annotation”, a page will open, where you can also enter the text of the annotation and select its privacy.
Thanks for the info: https://support.google.com :)