Yellow-staining mushroom
A poisonous Agaricus that may cause severe gastrointestinal symptoms.
Agaricus campestris
Русское название: Шампиньон полевой
A grassland relative of cultivated button mushrooms. Several white-gilled mushrooms are poisonous or dangerous lookalikes; casual comparison with a photo is not a safe basis for consumption. Habitats and microscopic traits matter.

Never decide to eat a wild mushroom from a photograph or online description. A mistake can be fatal. For mushroom ingestion or suspected poisoning, contact emergency medical services or a poison centre immediately, even if symptoms have not appeared.
Irish Poisons Centre mushroom safety ↗Europe and other temperate regions
Grasslands, meadows and pastures
Images and brief descriptions are for learning, not for reliably identifying a specimen. Take particular care with poisonous plants and mushrooms.
Identification is never guaranteed by a photo. Scientific names are used to reduce confusion between local names.