In ABAP you can use && sign to concatenate variables as below
hello TYPE string, world TYPE string, helloworld TYPE string. hello = 'hello'. world = 'world'. helloworld = hello && world.
If you want to concatenate strings directly, you can use
helloworld = 'hello' && 'world'.
If you want to keep space in between, you would require ` symbol as below
helloworld = hello && ` and ` && world