First and foremst, you should consider doing a bit of reading on the forums. You'll find all sorts of answers to anything that comes to mind...

1."t" in a motor refers to the numbers of turns or winds a motor has on each pole. So a 25t motor is a 25 turn or wind. without going into too much depth the lower the turn rating = the higher the rpm and lower the torque.

2. Generally and in most cases a 540 sized motor (most common size for 1/10th scale) can take around 7.4 volts. There are exceptions but those motors will have a spec sheet explaining their voltage intakes.

3. An esc (electronic speed control) usually has an amperage rating (25A in your example) which means it operates at its best when the batteries can supply at least the A rating. You'll see li-po batteries that give a C rating for discharge so if you multiply the capacity of the pack and the discharge rating you'll get how many amps the li-po pack can give your esc.

(example:5000mAh=5A..5Ax30C=150A discharge)

4. unless its a special high voltage servo, it normally takes 4.8 to 7.4 volts. If it isnt a high voltage servo, you can cause damage to it unless you have a BEC which can regulate voltage to the servo to appropriate levels.

5. Never put too much voltage and never mix packs of different voltage levels.

6. Depending on what type of pack you're using (Ni-MH or Li-Po) you'll see different cell descriptions.

Ni-Mh packs usually come in 6 or 7 cell packs which are 7.2 to 8.4 volt packs

li-Po come in all sorts of voltage levels and S type packs, the most common being 1S (3.7volts) 2S (7.4 volt) and 3S (11.1 volt). Some high powered packs can be found for speed controls that are manufactured for high voltage packs. (for example 1/8 scale electric brushless systems can take up to 6S packs (22.2 volts)

7. see #6 for voltage answers and see #5 for thoughts on voltage levels in esc...

Start reading up on all the information the forums can provide you...

welcome to the RC world, btw.