Outpost
An Outpost is a manned base on Mars. However, it is not a settlement because the residents are only temporary.
Reason for an outpost
We need experience living on Mars before we can colonize. We also need a manned presence on Mars. We should setup an outpost on Mars before even the first people arrive. When the time for colonization is right, the outpost will develop into a fully fledged settlement.
A perminant settlement will want to be close to resources, such as mineral ores. Early outposts can explore the area around them and locate these resources.
NASA and other space agencies have been very resistant to doing tests of Martian gravity on mammals (such as raising mice in a centrifuge on the ISS). These experiements can be done on Mars, which will inform the design of long term settlements. See Low gravity for more information.
Setup of an outpost
An outpost will be much like a semi-autonomous colony, albeit on a much smaller scale. Food, air, water and energy will be created in-situ. Crews could be replaced by a Manned Resupply mission