There are two ways to make an Obsidian Internal Link:

• Using the Wikilink format: [[Three laws of motion]]
• Using the Markdown format: [Three laws of motion](Three%20laws%20of%20motion.md)

You can also link to a specific heading of a note by using #. For example: [[Three laws of motion#second-law|Second law]].

Source: help.obsidian.md