Creating a WebPart is as simple as you create your custom control in ASP.net. Here the same logic will be applied but with advance feature.
To start developing with SharePoint solution, you need to understand the solution structure. Refer this
MSDN Article
Once you read it, you can take a look at this link for
Creating a Web part for SharePoint.
For your reference, take a look at this sample example link URL for
How to: Create a SharePoint Visual Web Part with Visual Studio 2012