This appears to be a rebranding of the free & open source LosslessCut.
videohelp[.]com/software/LosslessCut
LosslessCut is downloaded as a 7-Zip file, ran from wherever you expanded the 7-Zip file, though it's not portable -- files are added under C:\Users. Pazu Video Cutter itself by default is installed to Users\ [UserName]\ AppData\ Local\ Programs\, with additional folders in AppData\ Local & Roaming.
The idea is to slice & dice video files with audio, & glue pieces together, all without re-encoding, which takes time & loses quality. For joining files they have to be in the same format, encoded with the same settings. Video compressed for distribution [streaming, DVD, Blu-ray etc.] is made up of key frames, which are complete pictures, and a number of frames in between those key frames that just contain the parts of the image that changed. If you cut &/or join videos at key frames it's somewhat straightforward, and the only iffy part when joining clips is if the encoders & encoding settings match enough for it to work. If you try to cut or join video in between key frames software has to regenerate those partial frames, turning each one into a complete image, then re-encode just that part. That gets more iffy, as the encoding has to match more closely. [Encoder specs for whatever format ONLY cover playback hardware & software, NOT how the encoder operates or the exact format of the video.] That said, LosslessCut will let you cut or join in between key frames, and you can do it with ffmpeg from the command line as well -- it just may not work every time. Depending on the format, audio can get pretty dicey, especially AC3 -- it works best if the audio is in wave [.wav] or wave 64 [.w64] format.