Hi There!
Firstly, I agree with mcshine- don't get too bogged down with the bpm (but then it's not all bad knowing a little bit of theory and what is a bpm to explain things for you).
My advice to you is to understand the whole process of beatmatching and why you need to do it (a brief explanation is below but google it or search this forum and you'll be an expert by the end of the day).
There are basically two main methods of beatmatching -First is pushing the vinyl and then adjusting the pitch control; or Secondly "Advanced beatmatching" where you just adjust the tempo of the song using the pitch control. My advice is google "advanced beatmatching" and try beatmatching with that method first. It's also nice to have the first method in your pocket as well. From my experience, I've actually used both methods - I use advanced beatmatching but sometimes it goes out, so I use the first method to fine tune the tempo. Anyways, below is a brief intro of bpm and beatmatching.
The BPM
I'm sure you're a producer and I dont want to teach you how to suck eggs- basically it's beats per minute- how many beats there are in a minute. That's how we determine the tempo of a song (sort of like how we determine a speed of a car in miles per hour or kilometres per hour).
The connection between bpm and beatmatching is because DJs want to get the tempo (speed) of the beats the same (why do they want to do that? See below).
BEATMATCHING
The Theory
What beatmatching is is getting the BPM of two songs the same. The reason we do this is to get the beats in sync; this is because if it wasn't together, it would sound terrible (clash). Imagine how unimpressive marching soldiers that's not together would sound???
Example: You're a dj and you've been playing a nice dance song with extra cheese at 130bpm. You want to bring another track in but it's at 135bpm. Using the pitch controls on the second turntable, you would want to reduce it so the tempo of the second song is at 130bpm (you're making the second song slower by 5bpm). You're probably asking how on earth would you know what the bpm of these songs are?? In practice, you don't need to know. All you need to know is whether the song you're about to bring in ("cue in") is faster or slower than the song already playing - so you can match it (to the song already playing). Just like AdamEly's advice- "use your ears" and "practice, practice, practice!".