Meaning: We had a meal outdoors, beneath a large tree, consisting of sandwiches and fruit.
Choice of Words: Picnic: a meal eaten outdoors; Under: beneath or below; Big: large in size; Tree: a tall plant with a woody stem and branches; Eating: consuming food; Sandwiches: food items consisting of bread with fillings; Fruit: the edible part of a plant, typically sweet and fleshy.