Bash/sh - difference between && and ;

Question

I normally use ; to combine more than one command in a line, but some people prefer &&. Is there any difference? For example, cd ~; c

Answer 1

I'm using && because a long time ago at the nearby computer:

root# pwd
/
root# cd /tnp/test; rm -rf *
cd: /tnp/test: No such file or directory
...
... and after a while ...
...   
^C

but not helped... ;)

cd /tnp/test && rm -rf * is safe... ;)