I am finding it difficult to understand how the processes are launched in such a shell script

mainscript.sh

exec command1 &
sleep 10
exec command2 &
sleep 10

I understand that exec command does not create a new process it just replaces the bash with the command to be executed, in that case, what happens when it runs with an &

Currently I see this is the ps output something like this

UID      PID   PPID  C STIME TTY          TIME CMD
user+    1       0  0 16:43 ?        00:00:00 bash mainscript.sh
user+    48      1  9 16:43 ?        00:00:04 command1
user+    133     1  0 16:43 ?        00:00:00 command2