TCP/IP is acronim for Transmission Control Protocol / Internet Protocol. They are two main protocols used in modern networks.
They works on different layers of OSI model. IP protocol works on networking layer, and TCP on transport layer.
IP protocol is responsible for routing information through networks.
It provides addressing scheme. Every computer have unique address in network, so system can differentiate source and destination from other equipment on network, and also choose a path between. Using this protocol packets of data can be sent from source to destination.
It is used in LAN (Local Area Network) and WAN (Wide Area Network). IP is one of protocols applied on network layer. Other well known protocols on network layer are: IPX (Internetwork Packet Exchange), NetBEUI (not rutable, it can be used only in LAN), DDP (Datagram Delivery Protocol, AppleTalk), NWLink (Microsoft implementation the IPX/SPX)
TCP is connection oriented protocol. It means that it first establish connection between source and destination, before it start to transfer data. It cares that all data are delivered to destination, so we can say that it is reliable. To establish connection, it uses three way handshaking procedure.
Instead of TCP can be used UDP protocol. This is Lightweight protocol which doe not guarantee delivery. It is usually used for streaming media, etc.