Bulbs have to be separately purchased when buying lamps. The manufacturer shows some details of the recommended bulbs on the box of the lamp. However, there are features which have to be chosen by us. In a classic interior, the lighting has to be fit, so its accessories have to be chosen with care.
Threaded socket has two types: E27 (27 mm diameter) and E14 (14 mm diameter). Implicitly, only one of them fits for a given lamp.
The performance of the bulb is defined in Watt. The manufacturer displays instructions on the box maximizing the performance of the used bulb. Ordinary bulbs are between 40 and100 W, compact fluorescent lights are 5-20 W and LED bulbs are 0,5-15 W.
Flux (Lumen) is not given, we have to decide about it. This means, how strong the light of the bulb is. Bigger value means bigger flux.
Color temperature is also displayed on the box of every bulbs. It is given in Kelvin. The sunlight is about 5000 K, which is definitely cool light. Choose much warmer bulbs at home or else the output will be too rigid. The warm white light is 2700-3000 K, natural white is 3500-4000 K and the cold white is above 4500 K.
The shape of the bulbs is also important. For example, candle shaped bulbs should be chosen for a classic chandelier without lampshades. They can be purchased in opalescent white finish also. Spiral, energy-saving bulbs can be placed in chandeliers with opaque, closed bells. These need about 30-60 seconds from turning on to reach full light. If the lamp has open lampshades, choose bulbs fit inside the shade. Classic type bulbs can be purchased in LED version as well. The lifetime of these is longer.
So called Edison bulbs form a separate category. The filament is perfectly visible through the glass after turning it on. Its flux is low, it is suitable only for mood lighting. The color of its light is yellowish orange.
Specialists can always help, but it can be entrusted to the interior designer also.