Actuaries assess the probabilities of certain events occuring and the financial consequences of those events. Their work combines statistics and finance.
In general insurance, actuaries gauge the probability of the insured events occurring and the premiums needed to cover them. They also help devise insurance policies.
The funds of insurance companies and pension schemes require actuarial valuation in order to ensure that they are able to cover future liabilities. This is particularly important, and difficult, in the case of life insurance and pensions. The long term nature of the risk makes assessments very sensitive to the exact assumptions that are made. Assumptions that have to be made include investment returns and life expectancies.
Actuaries usually work either in the insurance industry or for firms of consulting actuaries. The demand in the insurance industry is obvious. Consulting actuaries are needed by clients such as company pension schemes.