Pict files can use 2 different forms of compression. 1- RLE Compression (the default) is lossless. 2- JPEG compression (only on some systems/graphics programmes) is lossy.

Lossless compression recreates a compressed file as an identical match to its original form. While lossy compression can't be used to compress anything that needs to be reproduced exactly.

File compression uses software algorithms to reduce file size by reducing the bit-rate of a file. Lossy compression takes it a bit further and lowers the quality of thr file to make it even smaller.

Lossy compression is commonly used for media files, but would not be appropriate for other types of files.

Lossless. Compression techniques do not remove detail from the image.