Why does AWS require me to specify an IP address for SSH? [on hold]

I'm launching an AWS EC2 instance, and in the Security Group configuration settings for an SSH rule, it asks for an IP source. Wouldn't I not want to specify an IP address, but instead an SSH key so that I could access my instance from anywhere while on my laptop?

Perhaps this is a personal misunderstanding of how SSH works; I'm hoping someone can shed some light on this.