You can categorize leads by their origin: inbound or outbound.
Inbound leads have expressed some interest in your brand, usually by filling out a form on your website, subscribing to your newsletter, or downloading a free resource. They have some awareness of your brand. They are much closer to being a sales qualified lead (SQLs) than outbound leads who are typically marketing qualified leads (MQLs).
Outbound leads are the ones you’ve reached out to first, usually through a cold call or email marketing. They have no awareness of who you are and can therefore be considered colder.