An appropriate way to practice ATC communications
Live ATC is an excellent way to listen and get familiar with your local airports procedures. I used to pick out a tail number and then pretended to be that aircraft. When ATC gave instructions, I would say back what I think the response should be.

If there are terms or phrases you dont understand, you should be able to look them up in the Pilot/Controller Glossary here:
https://www.faa.gov/air_traffic/publications/media/pcg_10-12-17.pdf

ATC and pilots should do their best to use the official phraseology in the glossary. However, the goal of communication on the radio should be clarity. If there is something you want to say but dont know how, just say it plainly without worrying about the 'official' wording.