The miter gauge slides in a slot parallel to the blade. It has a small fence adjustable between zero and 45 degrees to the left or right. At zero degrees, the fence is perpendicular to the blade.
The miter gauge makes simple crosscuts and miter cuts across the width of a board. To make an angled crosscut, the miter gauge fence is set to the angle. The miter gauge guides the board through the blade as the operator holds the board against the miter gauge fence.
A tapering jig holds the board at an angle for a long cut along the length of the board. There are two types. The first slides in one of the table's slots, similar to a miter gauge. The second slides against the main fence. Both types make the cuts accurately. Commercially manufactured tapering jigs are available, but many home woodworkers build their own using free plans from woodworking magazines or websites. Building your own allows you to adapt the design to your specific needs.
Most miter sleds are jigs built in the workshop. They slide back and forth on the table using both slots for exact miter cuts.
The sled is a flat board with guides that hold a board at a specific angle for a crosscut. The sled provides a place to clamp the board in place to prevent movement during cutting. Most miter sleds are not adjustable and only hold the board at one angle, but the cuts they make are repeatable and more precise than those made on a miter gauge.
Angle cuts on a table saw are more difficult than straight cuts because the board tends to move as it makes contact with the blade. Without a guide, holding the board at the correct angle is difficult and dangerous. An angle guide designed for the type of cut required makes the cut easier and less dangerous by keeping your hands away from the blade and holding the work piece precisely.