What is Partial Mash Brewing?
An option for beginning all-grainers is to take the transition half-way. Use a small mash to provide wort complexity and freshness, but use malt extract to provide the bulk of the fermentables. This option is particularly attractive for brewers living in small apartments with limited room in the kitchen for large pieces of equipment.
A partial mash is carried out just like a full scale mash, but the volume of wort collected is only the 3 - 4 gallons that you would normally boil when brewing with extract. The procedure is also similar to using extract & steeped specialty grain, the extract is added to the grain-based wort and the boil proceeds as usual.
What is a partial mash? PDF