The main difference is simple:
Posts appear in your blog feed and RSS. They're dated, chronological content—your articles, thoughts, whatever you publish regularly.
Pages are static, unlisted pages. Think About, Contact, or any standalone page you don't want in your main feed.
Press W anywhere to start a new post.
Or use the "New post" button and choose between Post or Page in the right sidebar.
Type – Post or Page. Pages are unlisted and don't appear in your feed or RSS.
Published Date – Set it to now, or schedule for later. If the date is in the future, it won't be visible until then.
Slug – The URL of your post. Auto-generated from the title, but you can change it.
Tags – Only for posts. Separate with commas. Used for organization and SEO.
Excerpt – A short description. Used as meta description for SEO and preview text when sharing.
Drafts are only visible to you. When you're ready, switch to Published and hit Save.
That's it.