This can be one that has many responses and an excellent question. At its most basic definition SharePoint is a net application from Microsoft that enables organizations to work better by allowing users share advice, data and files. There are multiple SharePoint services and products for businesses to choose from, each providing an unique set of benefits.
SharePoint Foundation is the free item which has the fundamental cooperation features including staff sites, document libraries, workflows, calendars, listings and more.
A list can have multiple columns much like a workbook in Excel or a dining table in MS Access or any database, and is exactly that, a list. It is possible to save information as rows and produce views to display the info in different modes through filters, sorting and grouping.
A document library is employed to save files and records and functions much like a list in that you may add the document to be tagged by columns and create views. You can also enable versioning of files in addition to have the ability to check out document for enhancing and checking them back in.
Workflows may be applied to items stored in listings or files stored in libraries. They’re able to be as simple as notifying an individual when the value of a column is up-dated or as complex as a procedure that includes dozens if not hundreds of steps and tasks.
Calendars are accustomed to keep track of events, appointments and meetings. You may add extra columns and it’s basically a sort of list, create views and implement workflows. You may also link Outlook calendars and overlay (push-down storage) SharePoint calendars on top of one another.
The point is it is possible to save details and all info related to one topic, thing or procedure within a website.
Further reading http://www.whatissharepoint.co.uk/