What is considered Intellectual property?

[gigo53]

I am working for a company right now that provides a notification service in LA. I've been there for over 5 years and pretty much know how the business operates and learned everything i needed to know. Is it legal to quit and then start up my own type of service? As far as using the same type of software and same methods and procedure? If my invoice/purchase order or disclaimer looked the same (which i do not intend on doing), would that be copying and get me in trouble? What can he sue me for if he finds out about my business, if anything? Is it no different from a waiter/cook quitting a restaurant to open his own?