What you can do with your ticket and what not.

So you have got your ticket (Semester Ticket, Deutschland Ticket), but what can you do with this ticket?
It is quite easy:

Allowed types of public transport

With your ticket, you are allowed to use any kind of regional transport
So those are:
– regional trains (RB, RE, S-Bahn, U-Bahn, Metro, Trams)
– regional busses (all busses except private bus companies (e.g. FlixBus)
– regional ferries

[!] Trains like IC, ICE, EC, ECE and international trains (like the polish ones) are NOT regional trains. (FEX for Berlin Airport can be used with regional tickets).
Those count as speed or international trains, and you always need to buy a ticket for them.

Where the ticket is valid

The Semester Ticket is valid for regional transport within the VBB network.
VBB means Verbund Berlin Brandenburg, any ticket that you get for VBB is valid in all of Berlin and Brandenburg.

The Deutschland Ticket is valid in all of Germany for regional transport.

Both the Semester Ticket and the Deutschland Ticket are valid every time, including weekends and holidays.

These are the tickets that you usually get through the university, tho, if you get tickets other than for VBB or for all of Germany, you have to be careful:
There are tickets for:
State (Berlin Brandenburg)
Province (e.g. Märkisch-Oderland, Landkreis Oder/Spree)
City (e.g. Frankfurt (Oder)

But for cities there are often different zones, like the zones A, B and C.
If you have a ticket for a specific zone in a city, you can only travel within that zone.
So you have to look up what the zone means, as example, zone A can mean in the city centre, while zone C means only on the outer edge of the city.

If you are unsure about your ticket, you can always ask the train conductors or at a service point.
Be careful and make sure that you always use a valid ticket, or else, you might get a 60€ fine and have to deboard the train immediatly.

Safe travel!