While both consecutive and simultaneous interpretation is different forms of interpretation services, there is a big difference between the two.
In the case of a consecutive interpretation service, an interpreter has to wait till the time a speaker has completed speaking his sentence. The interpreter then translates the words of the speaker in the target language. Ideally, when the setting is more formal, the segments get usually longer too. Thus the interpreters should be well trained in special memory techniques and develop and practice note taking.
Consecutive interpretation is most apt for all such cases when the group is smaller relatively and there is a need to provide a special personal touch. Some examples are teleconferences, interviews and business meetings. It could be also an exchange between only two persons.
On the other hand, simultaneous interpretation is an interpretation technique wherein the message is translated from the source to the target language as quickly as possible. This is a technique wherein the interpreter listens to the speaker, and provides immediate simultaneous translation in the target language even before the concerned speaker has completed speaking. This technique of interpretation is very popular in at international forums, particularly government level meetings like the United Nations or G10 meetings.