What is the difference between consecutive and
simultaneous interpretation?
In consecutive interpretation, the interpreter will wait for natural pauses to interpret the message. It is mostly appropriate for smaller gatherings such as conference calls, interviews and meetings because it doesn’t require equipment.
In simultaneous interpretation, the interpreter relays the interpreted message while  the speaker is talking. This type of interpretation requires equipment, typically a booth, microphones and headphones, as well as receivers with headphones for the audience.
Whispered interpretation is simultaneous and is done without equipment, but is appropriate only for particular situations where the client is not required to interact with the speaker.

How many consecutive or simultaneous interpreters do I need?
Interpreters generally work in teams of two or more, although this varies according to the venue. Interpretation is extremely demanding, so the team members tend to rotate every 20 to 30 minutes. In a booth environment, there will always be an active and an assistant interpreter alternating roles. While one interprets, the other interpreter provides words, phrases and terms when needed and makes sure the active interpreter has a clear sightline to any visual material.