が有(あ)るTo be, There is

がある is a common construction that is simply a combination of the が particle, and the う-Verb, ある. This expression means 'to exist', or 'there is', and is used in relation to non-living/inanimate things.

Because the things being described in these examples are not considered to be 'alive', ある is the verb that will be used. いる is used for living things.

The polite form of ある conjugates as あります. Due to the る changing to り, we can determine that ある is a う-Verb (Godan verb). However, ある is irregular in that the plain negative form is ない, not あらない.

The kanji form of 有(あ)る is quite common, and should be learned as early as possible, to save any confusion while reading. There is no nuance difference between this expression being used with, or without kanji, and is up to the preference of the writer.