a job card can span many lines, but there must be at least one step in a job.
Does it mean that a job statement with atleast a single step can be called as JOB CARD
A "skeleton" is a data set used by ISPF file tailoring. Whilst tailoring JCL is probably much the most likely instance, a skeleton need not have a single line in it that is intended to be JCL.
If Skeleton is a dataset, where is it located and in what name ? Can I browse this dataset ? What do you exactly mean by JCL tailoring as I am not able to understand by that term.