Federal Skilled Workers class (FSWC) is one of the 3 categories that fall under the Federal Economic Class ruled by Express Entry. And just like any other immigration program, candidates must meet the minimum requirements. The first step is to achieve the pass mark of the selection factors, which is 67 points out of 100. The table below shows a breakdown of the score (more details can be found here):

Based on this, the candidate is considered eligible to enter the pool of candidates. Now, the candidate will be assigned points based on his qualifications that are mentioned above and will be competing with the other candidates in the pool.
The Express Entry system, by holding bi-weekly draws, invites candidates who met or exceeded the CRS cut-off to apply for permanent residence. Normally this cut-off changes based on the scores available at that time in the pool and the objective number of the candidates to be invited.
Keep in mind that applying to this program cannot be done directly, the candidate waits until he is invited to. And that among other factors, the candidate needs to prove that he has sufficient funds to provide for himself and his family AND to be admissible to enter and remain in Canada.
in case if a skilled worker is interested in residing in Québec, the province has its own selection criteria and the program is known as “Québec-selected” skilled workers.