where is the former one used?
In fiberglass for insulation and structural materials
Boron
Boron is primarily used in chemical compounds. About half of all boron consumed globally is an additive in fiberglass for insulation and structural materials. 
what is referred to as a metalloid? It is a type of chemical element which has a preponderance of properties in between, or that are a mixture of, those of metals and nonmetals. where is it used commonly? In the literature of chemistry. what other names are given to it? "Amphoteric element," "boundary element," "half-metal," etc. can you give two examples of this element? Boron and silicon
wiki:1603037
Boron [SEP] Introduction
Industrially, very pure boron is produced with difficulty because of refractory contamination by carbon or other elements. Several allotropes of boron exist: amorphous boron is a brown powder; crystalline boron is silvery to black, extremely hard (about 9.5 on the Mohs scale), and a poor electrical conductor at room temperature. The primary use of elemental boron is as boron filaments with applications similar to carbon fibers in some high-strength materials. Boron is primarily used in chemical compounds. About half of all boron consumed globally is an additive in fiberglass for insulation and structural materials. The next leading use is in polymers and ceramics in high-strength, lightweight structural and refractory materials.