1. Consecutive

The speaker speaks, then he/she pauses for the interpretation, then the speaker speaks again. 

Plus: Interpretation will be in coherent, complete thoughts.  Korean language has grammar structure that would sometimes chop spoken English sentences into fragmented ones when simultaneously interpreted.

Seen here on the right is Yours Truly with Adm. In-Yong PARK, Vice-Chairman of the Chief of Staffs.  The venue was Chiefs of Defense (CHOD) conference held in Hawaii.  There were combined total of more than 100 stars at the conference.  You see, in Hawaii you can see stars during daytimes.

Plus: Does not require any special equipment.

Minus: Requires more time to complete the dialogue/proceeding.  The interpreter will have to speak about the same length of time as the speaker.  In a prepared speech or presentation, the time requirement would be approximately double the usual sans interpretation.  In dialogue or discussion sessions, the time requirement could be less than double since the interpreter will not require additional time that the speaker needs to collect his thoughts.

A skilled interpreter will be able to allow the speaker to speak in longer segments.

Recommended for : Highly technical subjects; instances where each word uttered could have significant meaning (i.e. political statement); depositions; consultations & meetings; and, negotiations.

2. Simultaneous

The speaker and the interpreter speak at the same time. 

The interpreter's voice is heard by only those with audio receiver.

Plus: Saves time.  When the speaker is done, so is the interpreter.

Minus: Accuracy is sacrificed for speed.  Especially true when numbers, abstract ideas, or esoteric terminologies are used.  (I love that word "esoteric."  It sound so...esotetic.)

Minus: Requires equipment: Transmitter for the interpreter and receiver for the listener are a must.  In addition, the speaker may have to wear a transmitter and the interpreter may require a soundproofed booth.

A skilled interpreter will be able to add accuracy to his/her interpretation by back-tracking in between the speaker's pauses. 

Recommended for: Conferences and seminars where the setting is content-rich but limited in time.

3. Whispering

Basically a simultaneous interpretation without the equipment.

Plus: Does not require any special equipment.

Minus: Can only be used when there are only 1 or 2 listeners. 
Minus: The listener may be confused by overlap of words by the speaker and the interpreter.  Especially true if the listener already has a good foundation in English.  (Technical term that describes the phenomena is "interference".)

Minus: If the interpreter has bad breath, the listener will be dead by the time the interpreter is done.  If the listener has bad body odor, the interpreter will be dead by the time the speaker is done.

A skilled interpreter will adjust to the English fluency of the listener and try to minimize interference that can lead to confusion (possibly resulting in less direct interpretation).

Recommended: For occasions requiring interpretation for only a brief period of time where consecutive would not be practical.  Otherwise, it's simply not a very good means of communicating.  Incidentally, this is the mode of interpretation adopted in courtrooms in the U.S. (Seems to work fine for European languages, but not as effective for Korean).