This is the tag for the "release group" (PSA Ritual) known for creating highly compressed, high-quality encodes.
This is a compressed archive file. To view the video, the file must be extracted using software like WinRAR or 7-Zip. Where to Watch Legally 9-1-1.S06E03.1080p.WEBRip.6CH.x265.HEVC-PSA.rar
This refers to the High Efficiency Video Coding standard. It allows the file to be significantly smaller in size without sacrificing visual quality compared to the older x264 standard. This is the tag for the "release group"