multi-tabling software

i apologize, i checked the search function but was barely sure what words to put in.. anyhow, not very successful.

i'd really appreciate a little help on something fairly simple.

my question is:

what do people use to multi-table on one monitor?? is there special software? or, do the sites' software have an option to multi-table on one screen??

it seems like it would more be something on your own computer...

can someone please help me on this?? i would be very thankful!! all i need is the name of a couple of products/websites.