sed > Stream editor allow filter and transform texts, find pattern and replace with whatever is that you want to replace with, it's like search and replace.

You can use other separators instead of slashes (/). Example pipe | or hash #

1 - sed substitution -- s for substitution. replaces only the first occurrence in each line of the file and save to a new file

sed 's/word/newword/' < oldfile > newfile

2 - replaces every occurrence of 'word'. g for global

sed 's/word/newword/g' < oldfi...