Give the landlord three pictures, throw a brick to attract jade.

As shown in the figure.

In the first picture, it is obvious that the left and right ends of the bulb are connected together (indicated by red lines), so that the circuit can be considered as parallel.

On the contrary, as shown in Figure 2, if the left and right ends are not connected together, but a wire passes through two bulbs from left to right, it is considered to be in series.

Although there is a switch K 1 in Figure 3, it does not affect the left-right connection of the light bulb L 1L2. Therefore, it is considered to be parallel.

A good way is to remember the formula "the left end is connected to the left end, and the right end is connected to the right end (parallel circuit)", and then connect the left and right ends to the positive and negative poles respectively. You can find similar questions to practice online. If you don't understand, you can Baidu Hi.