berlin train stations

HBF is the main train station, Bahnhof Zoo is the former main train station in the west, now no longer as important but still a train station. I've never heard about a Westbahnhof in Berlin, sorry I can't tell you anything about it.
.Anyway, Berlin has an excellent public transport system which connects all train stations.

ok thanks.im arriving at hbf and am staying near zoo station.is this distance walkable or whats the best way to get to my accommodation?

Hauptbahnhof and Zoologischer Garten are three stops from each other on S-Bahn Lines S5, S9 and S75.

It's probably not a walkable distance with luggage.

DB timetable
To: Berlin Zoologischer Garten

S-Bahn and U-Bahn network
From Hauptbahnhof (Hbf) to Zoologischer Garten (Zoo) you can use one of the many S-Bahn and regional trains serving this route. Distance is 3-4 km. Travel time is 5-6 minutes.

a) if you travel on a rail pass
S-Bahn and regional trains are covered
b) if you plan to use a normal ticket buy it to Zoologischer Garten station. Same price like to Hauptbahnhof.
c) if you use a special or global fare (nighttrain) ticket to Hauptbahnhof buy a short hop ticket (Kurzstrecke) for the S-Bahn (EUR 1,30).

The BVG site has more info on public transport in Berlin.

Take a look at your ticket (once you bought it). As destination, does it merely say 'Berlin', without further indication of the station? Then, as far as I know, you may use your ticket going to any station between 'Westkreuz' and 'Lichtenberg' stations (west-east mainline, this would include 'Zoo' abd 'Hbf') or 'Jungfernheide'/'Gesundbrunnen' to 'Südkreuz' (north-south mainline).

I think that even in case you clearly demand a ticket to 'Zoo', still 'Berlin' is likely to be printed solely due to this reason. Please note that other local transport (trams, busses, 'U-Bahn') is strictly excluded from this rule.

Trains/S-Bahn between 'Hbf' and 'Zoo' are running very, very frequently, no need to walk...

my ticket says berlin hbf.i will be arriving from zagan in poland.do you think the train will pass zoo station first,or continue to zoo?thanks for your help

no, it will not, lichtenberg is first major station trains from EAST use. then comes HBF. but as no trains (AFAIK) end at HBF, due to how its build, it will likely AFTER HBF stop at zoo, 5/10 mins later. double check place of htl: it most likely is not right besides ZOO, so maybe some other route may be feasible

DB timetable
From: Zagan
To: Berlin Zoologischer Garten

No direct trains. The systems rather suggests to change at Ostbahnhof.
But you can also change at Hauptbahnhof, as only from there you could use the short hop ticket to Zoo station (max. 3 stops for a short hop ticket).

thanks everyone for your help.im very grateful