examples:

Google

a widely used search engine that uses text-matching techniques to find web pages that are important and relevant to a user's search

Yahoo

a widely used search engine for the web that finds information, news, images, products, finance

Ask Jeeves

a widely used search engine accepting plain English questions or phrases or terms

type of:

computer program, computer programme, program, programme

(computer science) a sequence of instructions that a computer can interpret and execute