The term Cipher Suite stands for a collection of cryptographic methods used (encryption of information). This collection includes the key exchange procedure, the signature procedure, the encryption and cryptographic hash functions. This combination of cryptographic components ensures a secure connection between two parties, e.g. your mail program and a server. In the TLS protocol, the cipher suite (cryptographic procedure) determines which algorithms are to be used to establish a secure data connection and is responsible for the security of the connection.
The long-established RC4 encryption algorithm has been considered insecure for many years. Security researchers are aware of many critical gaps. In 2015, the IETF (Internet Engineering Task Force) banned the use of RC4 for TLS connections in RFC7465.