What is IP address?

IP stands for Internet Protocol. IP address is a unique number which is used to identify device within a network. Every device connected to a network (the Internet is a network too) must have IP address in order to communicate with other devices on the network. IP addresses are usually represented in dot-decimal notation: four numbers, each ranging from 0 to 255, separated by dots, e.g.

Can I find exact street address by IP?

No. Internet service providers (ISP) do not assign constant IP addresses to their customers because, unlike in the case with phone numbers, there is a limited number of available IP addresses. Instead, some ISPs shuffle internet IP addresses among currently connected customers as often as every several hours; others might leave them unchanged for days. By doing so ISPs decrease the number of IP addresses they need to use to serve their clients.

As a result, IP addresses are not assigned to some particular street or house but to a rather broad geographical region. However, in most cases it is possible to narrow the possible geographical location of an IP address down to 25 mile radius.

What reserved IP means?

IANA (Internet Assigned Numbers Authority) the entity which regulates usage of IP has reserved some IP address blocks that have limited or no usage outside of private networks or standalone computers.

Reserved and Special-Use IPv4 Addresses
Start IP End IP Description "This" Network Private-Use Networks Public-Data Networks Cable Television Networks Reserved but can be allocated Loopback Reserved but can be allocated Link Local Private-Use Networks Reserved but can be allocated Reserved but can be allocated Test-Net 6to4 Relay Anycast Private-Use Networks Network Interconnect DBT Reserved but can be allocated Multicast Reserved for Future Use

More information about reserved and special-use IPv4 addresses can be found on IANA's website.

Can I Find IP of an Email?

No. Email address is not associated with any geographical or IP address. Mail servers can usually be accessible from anywhere in the world by any number of people who know the password. Email service providers do know from what IP some certain email was sent but this information is normally kept private and is not legally obtainable (unless you have a warrant from court to obtain this information and the mail servers are in the country where this warrant can be enforced)