Ceiling and Floor

Can someone explain what they do? The forums don't seem to speak of them much, and I can't decypher their purpose.
They seem like they could be useful.

Here's the docs copied from Blitz3D:

Floor# ( y# )
Parameters
y = any number  

Description
Rounds downward, i.e. in the direction of -Infinity. 

It is a common mistake to think this simply sets everything after the decimal point to zero. 
But this is true only for positive numbers: 

Floor( 1.75 ) ....... 1.0 
Floor( -1.75 ) .... -2.0 

See also Ceil and Int for other types of rounding.  

Example
; Ceil / Floor / Int example, three kinds of rounding. 

; Move mouse. Escape quits. 

Graphics 640, 480 

Const KEY_ESC = 1 

SetBuffer BackBuffer() 
Origin 320, 240 

MoveMouse 320, 240 : HidePointer 

While Not KeyDown( KEY_ESC ) 

Cls 

my = MouseY() - 240 
Color 100, 100, 0 
Line -320, my, 319, my 

DrawNumberLine 

y# = Float( -my ) / 32 

Text 100, 50, " y = " + y 
Text 100, 70, " Ceil( y ) = " + Ceil( y ) 
Text 100, 90, " Floor( y ) = " + Floor( y ) 
Text 100, 110, " Int( y ) = " + Int( y ) 

Flip 

Wend 
End 

Function DrawNumberLine( ) ; vertical line with numeric labels 

Color 255, 255, 255 
Line 0, -240, 0, 239 

For n = -7 To 7 
yn = -32 * n 
Line -2, yn, 2, yn 
Text -30, yn - 6, RSet( n, 2 ) 
Next 

End Function  

Oh, so they can be used like rounding tools. I see. Thank you for your help, JimJams.