what is different "this"these"that"those"

"This" is used to indicate singular thing or person which we have near.(ex) this is my pen. 2)this is my brother. "These" is used to indicate plural things or persons which we have near.(ex)these pens are expensive 2)these are my classmates. "That is used to indicate singular person or thing, especially when he/she/it not near the person speaking.(ex) yesterday I lost my purse that was my lucky purse."Those" is plural of that,it remains same(ex) yesterday I gave you sweets those were my mom's preparation.