The word ‘Shaikh’ has diverse understanding in Islamic society.
In the Arabian Peninsula it is honorific title exclusive for the members of royal families.
In Sufism it represents Wali and the title is added to the name of Sufis out of respect of their followers. It can also designate wise and elderly person in society.
In the Indian subcontinent Shaikh is an ethnic title, lower in rank of Syed. But higher than Malik, Pathan or Ansari. The title Syed is exclusive to people of Prophet Muhammad descendants. But also who self-assume the title to claim superiority from those who are not. Yet there are God fearing Syed but hide the title as mark of respect for those non-Syed. Still in other cases, those who converted from Brahmin to Islam were entitle to a reciprocal title.
According to Madrassas convention the title is conferred to those who are given Ijazah (permission) to preach knowledge. Here is a website of shaikhs under this category: