Focus groups are neither a form of group interviewing nor serial interviewing. They generate information based on the give and take of group discussion rather than the one-way flow of regular survey interviews. The groups are usually homogenous, since combining participants with common interests, affiliations or backgrounds theoretically makes it easier to generate a useful or revealing discussion. A heterogeneous focus group, such as one incorporating hard-core conservatives and liberals alike, might either discourage some people from speaking freely or lead to verbal confrontations that exaggerate differences of opinion. A focus group's sample is neither randomly selected nor representative, so you cannot generalize results or compare them statistically.
Focus groups offer the palette with which to paint a deeper portrait of opinion in news stories.
They can complement, but not replace, good quantitative polling. For example, television news increasingly uses focus groups with diverse participants, whose responses can provide soundbites to illustrate trends found in traditional polls. The advantages to conducting polls on the Internet are obvious. A telephone poll may take several days and cost thousands of dollars, but an on-line poll can be ready overnight and for a fraction of the cost. On-line polls also regularly capture large numbers of responses, which might make them seem especially newsworthy.