The term 'portal' is used to describe a website that acts as an entry point or gateway to an array of services or resources.
Obviously all sites can do this to some degree, but typically a portal will have a wide range of resources, usually including a search facility, directory of other sites, news, e-mail etc. portals can be general (eg Yahoo) or be specific to a particular industry, occupation or field of interest. to choose which solution to go with that depend on your business