Most countries have a stock-exchange where you can trade the stocks of the various companies. If you are starting the investment game, the stock market just looks like a raw list of data (The list below represents the IBEX 35 which is the stock index of the Stock-Exchange of Madrid (source: www.bolsamadrid.es/esp/mercados/acciones):

ABERTIS SE.A ACCIONA ACERINOX ACS ALTADIS ANTENA 3 TV. ARCELOR BA.POPULAR BA.SABADELL BANKINTER BBVA BSCH CINTRA ENAGAS ENDESA FCC FERROVIAL GAMESA GAS NATURAL IBERDROLA IBERIA INDITEX INDRA A METROVACESA NH HOTELES PRISA R.E.E. REPSOL YPF SACYR VALLE. SOGECABLE TELECINCO TELEFONICA TELF.MOVILES TPI UNION FENOSA

If you take a closer look by adding some company information for each stock you could present the same list but sorted in a different way using (sector) categories. Which could look like the list below:

Companies in the area of infrastructure and communication: ABERTIS SE.A CINTRA TELEFONICA TELF.MOVILES

Construction and real estate sector: FCC FERROVIAL METROVACESA SACYR VALLE.

Companies in the area of commodities (Steel) ACCIONA ACERINOX ARCELOR

Tobacco industry: ACS ALTADIS

Entertainment, broadcasting (information distribution): ANTENA 3 TV. PRISA (amongst others the newspaper El Pais) SOGECABLE TELECINCO TPI

Financial services BA.POPULAR BA.SABADELL BANKINTER BBVA BSCH

Energy sector: ENAGAS ENDESA GAS NATURAL IBERDROLA R.E.E. REPSOL YPF UNION FENOSA

Transport and distribution: IBERIA INDITEX (Fashion, Textile)

(Industrial) Production: GAMESA (Wind Turbines) INDRA A (Software Development)

Business services - Hotel sector: NH HOTELES

Now that you have this list you can start the investment process; what sector(s) do I choose, and what stock would be the best for each sector...