trigger UpdateSpecificProduct on Product__c (after update) {

    List<Id> idProduct = new List<Id>{};

    for(Product__c p: Trigger.new){
        idProduct.add(p.id);
    }


    Specific_Product__c[] prodToUpdate = [select id 
                                            from Specific_Product__c 
                                            where Specific_Product__c.Product_ID__c IN :idProduct];

    {
        Description__c = p.Description__c,
        Availability__c = p.Availability__c,
    }

    update prodToUpdate;

}

trigger UpdateSpecificProduct on Product__c (after update) {

List<Id> idProduct = new List<Id>{};
Map<Id, Product__c> productDetails = new Map<Id,Product__c>();

for(Product__c p: Trigger.new){
    idProduct.add(p.id);
    productDetails.put(p.id,p);}


Specific_Product__c[] prodToUpdate = [select id,description__c, availability__c, Product_ID__c from Specific_Product__c where Specific_Product__c.Product_ID__c IN :idProduct];
for(Specific_Product__c specific : prodToUpdate){

    specific.Description__c = productDetails.get(specific.product_id__c).Description__c;
    specific.availability__c = productDetails.get(specific.product_id__c).availability__c

}

update prodToUpdate;

}