difference between sony nex-5 and DSLR ?


If you are considering the NEX 5 then also look at the Samsung NX system, which also uses APS-C sensors. IMO they offer a better alternative due to more lens options available. I think the new NX11 and older NX10 (should be a bargain now) handle very well and, with the new firmware upgrades, perform to a level where an entry level shooter may not have too much trouble.

Also consider micro four-thirds offerings like the Panasonic G-3. Despite the smaller sensor size they are also very good cameras.
 

TS... NEX-5/ or NEX-3 is mirrorless format camera. Mirrorless format cameras are generally small and very compact, like what many had mentioned before they are something like a compact camera with an APS-C or micro 4/3 sensor.

The mirrorless format camera is a totally different breed of animal as compared to the full DSLR, although IQ wise, they are very comparable to the DSLR, but DSLR (to me at least) offer better control and ergonomic. Also mirrorless camera, irregardless of their brand had less accessories available to them. People can argue to death which brand of mirrorless camera had more lenses and values, but values are subjective... and you don't need 100 lenses, you just need one or two.

Another format that is fast gaining recognisition is the SLT format... so far only Sony offer this excellent camera. They are not exactly big... but are not that small either. However speed wise, they are extremely fast (A55). They are the closest thing to a full DSLR in many case and surpass even some of the entry level DSLR too...

Anyway, before you jump into any format, be it DSLR, mirrorless or SLT, you would need to know full well of what you type of photography you want to shoot first before you do anything else.