People working in Venture Capital firms are called "venture capitalists". The background of venture capitalists varies broadly, but generally speaking, venture capitalists either come from a corporate or consulting backgrounds (they know how to run operations), entrepreneurial backgrounds (they' know how to start companies) or finance background (they know about managing investments). Titles in venture capital firms vary but there are broadly 5 categories:
Analyst
Those are the most junior professionals in the company, and usually have 1-2 years prior work experience, either with a startup, with an investment bank (very often focusing on Technology sectors) or with a strategy consulting firm. The key role of the analyst is to network, take part in industry and VC events, keep an eye on latest industry trends, and cold call potential target companies to try to find out about their business and obtain meeting with founders. They also might have some degree of involvement into the deal process (i.e. due diligence, market analysis, some valuation work) but their focus is largely on "origination". This is a very entrepreneurial role and analysts in VCs are often very well connected and aware of the latest happenings in the industry.
Analysts can be promoted to the associate level after a couple of years, but many of them choose to do an MBA or go the entrepreneurship route, founding their own businesses.
Associate
Associates are the next level in the hierarchy, and are on the "partner track", which means that they are expected to stay until they make it to partner.
Associates are usually ex bankers, consultants, investment professionals (i.e. private equity, other VC funds) or operational people with 3-5 years experience, sometime with an MBA or a PhD. The role is more focused on due diligence, analysing business plans, executing transactions, analysing interesting industry subsectors and helping out portfolio companies. It is the more analytical and deal making role within the VC fund.
Associates usually get promoted to principal after a few years of successfully executing deals. Some of them also leave to create their own businesses.
Principal
Principals are in charge or making portfolio companies run smoothly and will be on the board of a few portfolio companies. In addition, their role is to network and identify interesting opportunties for the fund, negotiate terms of acquisitions and also exit portfolio companies successfully.
Principals tend to stay until they are promoted to partner level, which happens once they have proven their ability to generate good deal for the firms and generate returns.
Partner
Partners and Principals have very similar roles in the firm. However partners tend to be less involved in the day to day deal making and are more focused on high level tasks such as identifying key sectors to invest in, giving the green light for investments and exits, sitting on the board of some portfolio companies, networking at a high level and representing the overall firm, as well as raising money for the firm (every 5-7 years) and commucating performance to investors.