Rob I think Linkedin like Facebook is some sort of social network site. I get loads of them too. I don't understand the need for it so I just delete everything that comes through. Ron
As Ron says, it's some sort of Face-ache thing but instead of being for teenagers, it's for people who think they're impotent (or important, I'm not sure which) and apparently they use it for 'networking'.
A sort of on-line Freemasonry without the wobbly handshakes.
As with Facebook, if you don't tell it not to, it will regularly weasel its way into memebers' contact lists and send them all an invite, quite often with the perpetrator not being aware of it.
You are correct, it's a site used in industry for people to network and to let potential employers see what they do, or have done. Often used by people who do a lot of contract work.
I don't have an account myself, but I know people who do. It's a handy tool to look people up who may be about to interview you if you are applying for a job with their company. Some people find it a great help, myself, I've got this far in life without it!