1.Features: SharePoint Features is part of Packaging and Deployment in SharePoint 2010 Features make it easier to activate or deactivate functionality in the course of a deployment, and administrators can easily transform the template or definition of a site by simply toggling a particular Feature on or off in the user interface.
2.Web Template: Web template refers to new feature element available in SharePoint 2010, which provides us flexible way to define definition (onet.xml file), which will be used only on provisioning time, when the site is created. There are no references to the definition on runtime, which provide easy maintainability for the definition. Source
3 Site Template: SharePoint site templates are pre-built definitions designed around a particular business need. You can use these templates as they are to create your own SharePoint site and then customize the site as much as you like. You’re probably familiar with the default site templates, like Team Site, Blog site, and Group Work Site as shown here.
In addition to the default templates, you can create your own site template based on a site you’ve created and customized in SharePoint. This is a powerful feature in SharePoint that allows you to create a custom solution and then share that solution with your peers, the broader organization, or outside organizations. You can also package the site and open it in another environment or application like Microsoft Visual Studio and further customize it there.
Devendra Velegandla is a five-time recipient of Microsoft's Most Valuable Professional (MVP) award (2014-2019) for Office Apps and Services, Office Servers and Services MVP and SharePoint Server. He received the MCC award for his contributions in Microsoft MSDN/TechNet forums. He loves sharing articles, videos, and tutorial on SharePoint and Office 365.