TTT

For Embroidery thread the higher the number the lighter weight it is.
For Example:
30 weight heavier weight
40 weight normal
60 weight lighter weight.

Remember most embroidery thread is 2 ply - meaning 2 stands of thread make up the thread.

EastWitch2

WHICH IS BETTER?

Heavier/thicker thread will fill more. It might look fuller or puffer. So it all depends on your design and the look you want.i use 40 most of the time.

I use the 60wt for my bobbin thread.

the higher the number the thinnest the thread...I wish it could be the same with me!!!!! hahahahahaha***

I think the best thing you can do is to check each design's information given by the digitzer as that would give the best stitch out of the design.

Most times digitizers digitze a design for use with 40 weight embroidery thread.
They may digitze certain design for use with a different weight of thread so always check the information for the designs.

This doesn't mean you couldn't use a different weight of thread for that design.
You might have problems with a lighter thread as it may not fill the design as nicely or form the type of stitches right in the design as a 40 weight thread would.

And using a heavier weight might cause thread problems such as thread breaks as the thread may just be too heavy for the type of design and the type of stitches in the design and could make the design too dense.

EastWitch2