What type of information does an .sf file contain? 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