VERY strange spam emails?

Hi, I was just wondering if someone could explain the origin of some of these weird spam emails I've been getting. The message will come from a normal looking email address (albeit one that isn't in my contact list from a previous conversation) and always gets put into my junk folder, but I sometimes look at them just to make sure. They often say stuff like "I'm going for a run today, are you coming with me?" followed by a bit.ly address or a similar link. Sometimes hotmail says the email is from just a name like Dave or Cynthia, and sometimes when I look at the email more closely it says it was sent to an email address other than mine - which makes no sense at all!? Once I got one that had my name followed by a question mark for the subject and the message just said "from flat 1?". They really vary in content. I figured that since they all have a dodgy looking link at the end of them, they are genuinely junk and not serious emails, but I just wonder what the weird messages are all about. I thought maybe its a method of trying to trick spam filters by disguising themselves as normal emails?

I dunno, but if anyone could shed some light on it I'd really appreciate it! Thanks!