I recently joined an agency online and was asked to send them money to register and use their services of work. I need to know that they are a real company how do I check this?

If you have to ask if they are real or not, they're not.

What kind of company is it?

If you have to pay someone to provide work for you its 99% a scam.

Most internet "work" programs are scams to start with, almost all of them where you have to send them money are.

Give us their name and web site and we will research them
What type of busienss are they

It's a real business. The question is "is their business taking your money"

It is.

You can Google the name of the business followed by better business bureau and see if any hits come up

It's not 100% but you can see if others complained