For video and animation, most artists use either 24 or 30 FPS. Since

animations can also consume many resources, Blender limits the total

length with a start and end frames. Above the frame rate settings, you

can set the start and end frames in your current scene (Figure 7.2).

Figure 7.2 - Start and end frames

Those values always start with 1 and 250 for start and end, respectively.

If you have to create an animation with 3 seconds using a 30 FPS,

which requires 90 frames, you can keep the start to 1 and set the end to

90.

If you don't change the start and end, all animations in Blender will occur

between frames 1 and 250. You can still create a 90 frames animation

and don't touch the start and end frames.