In its simplest description El nino& la Nina are climatic/oceanic events caused by reversed pressure systems in the west & east of the Pacific ocean.
These changes alters global climate.
*La Nina*
La Nina is where moisr air rises & condenses in the West Pacific (Philippines, Indonesia etc). High rainfalls across this regions (low pressure) are experienced & also globally. The heated air descends in the East Pacific (Chile, Peru etc) giving dry & hot conditions (high pressure). This is the *normal* circulation of air.
*El Nino*
The reverse occurs.
Air now rises & condense in the East Pacific (low pressure) & descends in the west (high pressure).
Dry & hot conditions experienced in the west Pacific & globally.
So I guess you can come with effects of these two as you now know what they are .
El Nino effects include:
droughts
heat waves
starvation
diseases etc
melting ice sheets->rise in sea level->flood
La Nina negative effects
Flooding by high rainfalls.
Read more here
https://thegeoroom.co.zw/climatology/el-nino.php
Some la Nina effects:
water borne diseases
Vector borne diseases e.g malaria
landslides