A Manned mission to Mars is a first step in the colonization process. There are two types of mission, a one way mission, with planned death or the start of a colony, and a Manned two-way mission. A one way mission is cheaper, but a two way mission will likely be a first step to developing a colony on Mars.
Manned mission will probably be preceded by unmanned missions.
NASA baseline missions
SpaceX, making humanity a multiplanet species