Bootstrap is the most popular CSS Framework for developing responsive and mobile-first websites.
SCSS is a preprocessor scripting language that extends the capabilities of CSS by adding features such as variables, nesting, and mixins. It allows developers to write more efficient and maintainable CSS code, and helps to streamline the development process by reducing repetition and increasing reusability.
A UI kit provides developers with a set of reusable components that can be easily integrated into a website or application. These components are pre-designed with consistent styling and functionality, allowing developers to save time and effort in the design and development process. UI kits can be either custom-built or third-party, and often include components for buttons, forms, typography, icons, and more.