Sow

Sow[e] specifies that e should be collected by the nearest enclosing Reap. 

Sow[e,tag] specifies that e should be collected by the nearest enclosing Reap whose pattern matches tag. 

Sow[e,{tag1,tag2,…}] specifies that e should be collected once for each pattern that matches a tagi. 

Please visit the official Wolfram Language Reference for more details and examples on core symbols.