what does the boolean modifier do exactly in blender?
If you want to simply join meshes into a single mesh see how to join two separate meshes or objects in blender
while the join tool lets you join two object of the same type into a single object, booleans in blender only work with meshes and the main difference between using booleans and joining meshes is you are not left with a separation gap between the two meshes or intersecting faces if objects are close to one another
Using booleans in blender
open a new blender object don’t delete the default cube or delete it and add a new cube if you that type of person which i am but don’t be like me
we also need another mesh object to use as the boolean object so lets add a uv sphere use the shortcut shift + A then select mesh then add uv sphere
this will add the sphere at the location of the 3d cursor which is the red white cross hair.
by default its position will be at 0,0 which is the same location as our cube so move the sphere a few points on the y direction by selecting the move tool from the tools menu
move the sphere but let it intersect with the cube by a bit so we have some interesting results if you have the objects far from each other that they are not intersecting then there is no point in using booleans you might as well just use the join tool.
for interesting results will keep them intersecting
select the cube then go to the modifiers and in the modifiers dropdown list find boolean
now add the boolean and in the boolean options under object type in the name of the sphere or just use the eye dropper to select it from the view port.
with that congratulation you have done your first Boolean operation in blender, select the sphere and hit H on your keyboard to see the results
the boolean operation you have done is the difference operation, select the cube again and go back to the bolean modifier and play around with the operation change them to intersect and union and difference, these are the 4 boolean operations in blender.
you still have control of the boolean object which is our sphere so you can unhide it at anytime scale it, rotate it or move it to see the results you get make sure to hide the sphere or apply the boolean modifier by clicking apply on the modifier to see the final results