Is there a difference between BMX and Motocross??

Okay I was wondering what the difference is, cause I want to do either one of them but I need to know what each one basically is so I know which would be right for me.

Also are BMX bikes or Motocross bikes expensive? Usually how much for a good err beginner one.

Sorry if I sound stupid, I just started looking into stuff like this...

motocross= involves dirt bikes, which have engines, cost a lot more.

bmx= involves pedal bikes, no engine, significantly less than a dirt bike.

Motorcross will probably more difficult to start off with but will get more fun. MotorX is basically riding over different terrain (jumps) the fastest. It is difficult jumping but then gets easier.
BMX isnt as expensive but is probably more physical as you have to really pump your legs.
Also MotorX has a higher risk, injury factor

yes there is a difference i do motocross mini leagues at 12(mini 125cc) and cycling leagues too. if your starting do bmx thats what i started off at. a good starting bike would be around 450$-800$ and if you started dirtbiking first for a good starter it would be my preference of a honda cr125r hondas the best its base price is $5,499 ok thanx for asking mate im australian but live in us