Notable Differences

Separate commands for Batch and Interactive jobs

Unlike PBS, in Slurm interactive jobs and batch jobs are launched with completely distinct commands.
Use sbatch [allocation request options] script to submit a job to the batch scheduler, and sinteractive [allocation request options] to launch an interactive job. sinteractive accepts most of the same allocation request options as sbatch does.
No need for cd $PBS_O_WORKDIR

In Slurm your batch job starts to run in the directory from which you submitted the script whereas in PBS/Torque you need to explicitly move back to that directory with cd $PBS_O_WORKDIR.
No need to manually export environment

The environment variables that are defined in your shell session at the time that you submit the script are exported into your batch job, whereas in PBS/Torque you need to use the -V flag to export your environment.
Location of output files

The output and error files are created in their final location immediately that the job begins or an error is generated, whereas in PBS/Torque temporary files are created that are only moved to the final location at the end of the job. Therefore in Slurm you can examine the output and error files from your job during its execution.

See the official Slurm Documentation for further details.