Jig Saw (Sabre)
The jig saw is used predominantly when cutting 
material that goes under door casings after they are undercut with a jamb saw. Other uses include cutting wood flooring around electrical floor outlets. More uses for this tool include making dual cuts on the same board with two different angles or scribed lines that are not straight. The list goes on with larger layouts.
Rips Long Boards On Small Layouts
For those that may have small layouts, the jig saw can also be used for ripping down full length boards if you don't want to include the cost of a table saw on your tool list. This occurs near the end of the installation against the wall parallel from your starting point. For thin engineered hardwoods, lower priced jig saws can handle the work, but using harder exotic species, more power and quality is needed, unless you can settle for a jagged cut.
Baseboard or quarter round will cover the last board wall rip cut, so there's really no need for a precise straight line cut. However from my experience, you may run off your scribed line on the last board if you're not patient or don't have the power to make a good cut. Occasionally once you fit the last board(s) into place while using a scrap piece of molding checking for coverage, a few gaps will appear. Trim does not cover. This is directly related to the cut made.
Tool Tips
Use care when cutting prefinished floors with a jig saw by not allowing too much pressure on the saw itself. The underside carriage of the saw that glides over the work can mar or ding prefinished hardwoods and their finishes. Often professionals will cover the underside with protective tape. When choosing a jig saw you may want to look at the length of the cord. Cheaper lower price saws have minimum lengths. Often you'll need to buy an extension cord.
Variable Speed Perfect For Floors
The more preferred jig saws have variable speed options that can improve your cutting appearances. Other options include an oscillating feature that allows the tool to either cut through the material quicker or slower, without the need for precision. This could be an option for smaller layouts that require very little rip cutting.
Blades available for these kinds of tools are numerous. From fine wood scroll like cuts, to cutting thinner metal and tubing.
