This is equivalent to seq 1 10, but portable. seq is not a standard tool and as such it may not exist in all systems, in fact it is discouraged as of today. Other variations to emulate various uses with seq:

# seq 1 2 10
for ((i=1; i<=10; i+=2)); do echo $i; done

# seq -w 5 10
for ((i=5; i<=10; ++i)); do printf '%02d\n' $i; done