Well there's a lot of endings for the -te form..
For example, you can add -iru (-inai, -masu, -imashita, -imasen deshita etc), which is called the progressive form.
So, if "oshieru" is the dictionary form of the verb "to teach/tell", then "oshiete" is the -te form.
So "oshieteimasu" could mean, depending on the context, "I am teaching".
"Ima watashi wa oshieteimasu" = "Now, I am teaching"
Also you can add "-kudasai" on the end of a verb in its -te form, to form a request.
"Oshietekudasai" = "Please tell me".
You'll learn more about this as you study, I can't write an exhaustive list here (not that I know all the ending anyway).
Here's a good website with lots of verb endings:
http://www.timwerx.net/language/jpverbs/index.htm