What is an .sf file. What information does it contain?
You should provide more context, otherwise one can only guess what is it you are looking for! In case you are asking about
Salmon's output, below is from their documentation:
Salmon’s main output is its quantification file. This file is a plain-text, tab-separated file with a single header line (which names all of the columns). This file is named quant.sf and appears at the top-level of Salmon’s output directory. The columns appear in the following order:
Name Length EffectiveLength TPM NumReads