laid-back as opposed to driven and high-energy

either a relaxed, laid back, accepting personality or a blood type.

relaxed personality: a patient and friendly person ( often used before a noun) - "a type B personality"

http://encarta.msn.com/.../...onaryResults.aspx

of, pertaining to, or designating a personality or a person characterized by serenity, relaxation, and contentment, and thus considered to be relatively unlikely to incur heart disease.

http://www.wordsmyth.net/live/home.php

http://www.bartleby.com/61/64/T0446400.html

(Psychology)
1. of or pertaining to a pattern of behavior characterized by an unhurried, patient, tolerant manner, an ability to relax easily, and amiability, and possibly associated with a decreased risk of heart disease.

2. of or pertaining to a person who exhibits Type B behavior.

http://www.infoplease.com/dictionary/Type+B

1) the blood group whose red cells carry the B antigen

2) relating to, characteristic of, having, or being a personality that is marked by a lack of excessive aggressiveness and tension and that has been implicated by some studies as a factor reducing the risk of cardiovascular disease <type B behavior>

http://dictionary.reference.com/search

Type B personality is a term used to describe people who tend to be

Relaxed
More likely than a Type A personality to be patient
Creative and imaginative
Inclined to self-analyze
In the 1950s, the cardiologist Meyer Friedman argued that risk of heart disease is greater in Type A personality people than in Type B personality people.

http://en.wikipedia.org/wiki/Type_B

Person who has a mellow personality.

http://www.moneyglossary.com/

Brachydactyly type B.

http://en.wikipedia.org/wiki/Brachydactyly_type_B

My Boyfriend is Type B (B-hyeong namja chingu) is a South Korean romantic comedy film for the year 2005. The basic premise of the film comes from the Japanese blood type theory of personality, which claims that a person's blood type can determine their personality traits. The heroine is type A (conservative and introverted) while her love interest is type B (passionate and irresponsible).

http://en.wikipedia.org/wiki/My_Boyfriend_Is_Type-B

s. arabinotarda type b

http://www.mercksource.com/.../...zSzdmd_s_10zPzhtm

type b tapping screw

http://www.allmetalcorp.com/htm/pg8_8_00.htm

type b w gas vent

http://www.hearth.com/what/glossary.html

An academic grade awarded by some institutions. Slightly better than a C+, slightly worse than a B.

http://en.wiktionary.org/wiki/B-

http://en.wikipedia.org/wiki/B_%28disambiguation%29

yeah, i was gonna say, in what context do you mean...
there could be a few answers for this, otherwise.

It can refer to a blood type.