From the Introduction [1]

    Many container platforms are available, but Apptainer is focused on:

    Verifiable reproducibility and security, using cryptographic signatures, an immutable container image format, and in-memory decryption.

    Integration over isolation by default. Easily make use of GPUs, high speed networks, parallel filesystems on a cluster or server by default.

    Mobility of compute. The single file SIF container format is easy to transport and share.

    A simple, effective security model. You are the same user inside a container as outside, and cannot gain additional privilege on the host system by default. Read more about Security in Apptainer.