The Seurat manual does a good job explaining the parameters for any function.
min.cells Include features detected in at least this many cells. Will subset the counts matrix as well. To reintroduce excluded
features, create a new object with a lower cutoff.
min.features Include cells where at least this many features are detected.
The values they picked here are somewhat arbitrary, but min.cells helps limit the number of genes used by removing those unlikely to play any part in differentiating groups of cells due to being expressed in very few cells. In general, most genes removed will be those with zero counts across all cells. min.features removes dead cells cells and empty droplets where few genes are detected.