A single-file kitchen (also known as a one-way galley or a straight-line kitchen) has all of these along one wall; the work triangle degenerates to a line. This is not optimal, but often the only solution if space is restricted. This may be common in an attic space that is being converted into a living space, or a studio apartment.
The double-file kitchen (or two-way galley, corridor kitchen) has two rows of cabinets at opposite walls, one containing the stove and the sink, the other the refrigerator. This is the classical work kitchen and makes efficient use of space.
In the L-kitchen, the cabinets occupy two adjacent walls. Again, the work triangle is preserved, and there may even be space for an additional table at a third wall, provided it does not intersect the triangle.
A U-kitchen has cabinets along three walls, typically with the sink at the base of the "U". This is a typical work kitchen, too, unless the two other cabinet rows are short enough to place a table at the fourth wall.
A G-kitchen has cabinets along three walls, like the U-kitchen, and also a partial fourth wall, often with a double basin sink at the corner of the G shape. The G-kitchen provides additional work and storage space, and can support two work triangles. A modified version of the G-kitchen is the double-L, which splits the G into two L-shaped components, essentially adding a smaller L-shaped island or peninsula to the L-kitchen.
The block kitchen (or island) is a more recent development, typically found in open kitchens. Here, the stove or both the stove and the sink are placed where an L or U kitchen would have a table, in a free-standing "island", separated from the other cabinets. In a closed room, this does not make much sense, but in an open kitchen, it makes the stove accessible from all sides such that two persons can cook together, and allows for contact with guests or the rest of the family, since the cook does not face the wall any more. Additionally, the kitchen island's counter-top can function as an overflow-surface for serving buffet style meals or sitting down to eat breakfast and snacks.