Timeline

A .3ds or .i3d model with an animation plays it in the 3D View, with a timeline along the view's foot. Only how the model's shown changes: its UVs and the file stay as they are.

An animated model in the 3D View, its timeline along the foot paused at frame 24

The ruler

The frames are numbered along the top, with each key in the file marked as a diamond. The playhead shows the frame showing: click or drag on the ruler to go to a frame. With the ruler focused, the arrow keys step a frame, or ten with Shift.

The buttons

Under the ruler, from the left:

Frame: the frame showing. Type one to go to it.
Go to the first frame, go to the previous key, play or pause, go to the next key, and go to the last frame. Playing goes round and round.
fps: how many frames a second it plays at. It starts at the file's own rate, 30 for a .3ds and 100 for an .i3d. Type another to play it faster or slower: the file keeps its own.

Seeing the UVs move

Picking and the textures follow the model as it moves, so a texture shows where it lands on each part as it turns. The UV Layout doesn't change: UVs don't move with an animation.

Saving a frame

Saved as OBJ, or as a new .3ds, the model comes out posed at the frame showing. Saved back into its own file, its animation comes through whole.