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