The document discusses the ulimit command, which is used to set resource limits for users on Linux systems. It lists the different options for ulimit like -n to set the maximum number of open files, -u for the maximum processes per user, and -t for the maximum CPU time. It then explains that exceeding these limits through things like a fork bomb, which is a denial of service attack where a process continuously replicates itself, can slow down or crash a system through resource starvation. Examples of fork bombs in different programming languages like Bash, Python, and Brainfuck are also provided.